# Battery Pack temperature sensor (Thermistor)

S

#### Spehro Pefhany

Jan 1, 1970
0
Hi, all:-

Is there any standard for the thermistor used in battery packs?
10K? B=????

Best regards,
Best regards,
Spehro Pefhany

G

Jan 1, 1970
0
S

Jan 1, 1970
0
G

#### Greg Neff

Jan 1, 1970
0
Thanks, Greg.

Unfortunately, that B (3435 +- 1%) is not very widely available. 8-(

Best regards,
Spehro Pefhany

That's why everyone uses the Semitec parts. You should be able to get
them here: http://www.paltronicsltd.com/linecard.php

I don't know how the spec was approved using a single-source part.
This is a perfect example of how not to specify a component within a
spec.

================================

Greg Neff
VP Engineering
*Microsym* Computers Inc.
[email protected]

S

#### Spehro Pefhany

Jan 1, 1970
0
That's why everyone uses the Semitec parts. You should be able to get
them here: http://www.paltronicsltd.com/linecard.php

Thanks, well do so.
I don't know how the spec was approved using a single-source part.
This is a perfect example of how not to specify a component within a
spec.

That particular Japanese company is one of the most experienced in the
thermistor field (the first by a long shot to develop very cheap yet
high precision parts AFAIR), but youd think there would be second
sources..

Best regards,
Spehro Pefhany

B

#### Ben Jackson

Jan 1, 1970
0
Unfortunately, that B (3435 +- 1%) is not very widely available. 8-(

Why in the world would you care about your battery temp to 1%? Isn't
the point just to avoid setting them on fire with the charger?

G

#### Greg Neff

Jan 1, 1970
0
Why in the world would you care about your battery temp to 1%? Isn't
the point just to avoid setting them on fire with the charger?

Well, yes and no. Another problem is cold temperature charging, which
can damage cells, reducing the capacity. Also a B value tolerance of
1% does not directly translate to a temperature accuracy. See:
http://www.semitec.co.jp/RT/AT/103AT1_11.xls

The Smart Battery Data Specification requires that the smart battery
be able to report temperature with an accuracy of ±3°K. So, you need
an accurate thermistor to meet this performance requirement. I don't
know the origin of the requirement.

================================

Greg Neff
VP Engineering
*Microsym* Computers Inc.
[email protected]

R

#### Rich Grise

Jan 1, 1970
0
That's why everyone uses the Semitec parts. You should be able to get
them here: http://www.paltronicsltd.com/linecard.php

I don't know how the spec was approved using a single-source part.
This is a perfect example of how not to specify a component within a
spec.

Well, what do you expect from a passel of bureaucrats? If they knew
their elbow from a hole in the ground, they wouldn't have got the job
of bureaucrat in the first place. ;-)

Cheers!
Rich

S

#### Spehro Pefhany

Jan 1, 1970
0
Well, what do you expect from a passel of bureaucrats? If they knew
their elbow from a hole in the ground, they wouldn't have got the job
of bureaucrat in the first place. ;-)

Cheers!
Rich

Ishizuka`s representative probably wrote that part of the spec. ;-)

Best regards,
Spehro Pefhany

R

#### Richard Henry

Jan 1, 1970
0
Well, yes and no. Another problem is cold temperature charging, which
can damage cells, reducing the capacity. Also a B value tolerance of
1% does not directly translate to a temperature accuracy. See:http://www..semitec.co.jp/RT/AT/103AT1_11.xls

The Smart Battery Data Specification requires that the smart battery
be able to report temperature with an accuracy of ±3°K. So, you need
an accurate thermistor to meet this performance requirement. I don't
know the origin of the requirement.

During a design review I stated that my heater-control thermistor
circuit could sense the temperature on a display within 5 degrees C.
When I was asked if that was good enough, I replied "We're not making
beer".

S

#### Spehro Pefhany

Jan 1, 1970
0
During a design review I stated that my heater-control thermistor
circuit could sense the temperature on a display within 5 degrees C.
When I was asked if that was good enough, I replied "We're not making
beer".

What *were* you making?

Best regards,
Spehro Pefhany

F

Jan 1, 1970
0
S

#### Spehro Pefhany

Jan 1, 1970
0
Whoa, what incredible performance, wonder how much they run in small
quantity.

There are lots of very inexpensive 1% thermistors these days,
especially in SMT (eg. 0402). I'd be interested in how they
manufacture bead thermistors to that tolerance, considering they
change more than 4%/Kelvin.

Best regards,
Spehro Pefhany

J

#### Jim Thompson

Jan 1, 1970
0
On Thu, 06 Sep 2007 08:45:53 -0400, Spehro Pefhany

[snip]
There are lots of very inexpensive 1% thermistors these days,
especially in SMT (eg. 0402). I'd be interested in how they
manufacture bead thermistors to that tolerance, considering they
change more than 4%/Kelvin.

Best regards,
Spehro Pefhany

4%/°K ? Seems high?

...Jim Thompson

S

#### Spehro Pefhany

Jan 1, 1970
0
On Thu, 06 Sep 2007 08:45:53 -0400, Spehro Pefhany

[snip]
There are lots of very inexpensive 1% thermistors these days,
especially in SMT (eg. 0402). I'd be interested in how they
manufacture bead thermistors to that tolerance, considering they
change more than 4%/Kelvin.

Best regards,
Spehro Pefhany

4%/°K ? Seems high?

...Jim Thompson

coeff ~= (B/T^2) = +3.8% for B = 3435 @ 300K (Semitec)
= +4.7% for B = 4250 @ 300K (Murata)

Best regards,
Spehro Pefhany

R

#### Richard Henry

Jan 1, 1970
0
On Wed, 05 Sep 2007 13:16:32 -0700, Richard Henry

What *were* you making?

Ruggedized displays.

S

#### Spehro Pefhany

Jan 1, 1970
0
Ruggedized displays.

Ah, I see. I thought you were displaying the measured temperature (my
usual requirement) rather than measuring the temperature of the
display!

Best regards,
Spehro Pefhany

R

#### Richard Henry

Jan 1, 1970
0
Ah, I see. I thought you were displaying the measured temperature (my
usual requirement) rather than measuring the temperature of the
display!

We could have gotten a more accurate measurement of the display
temperature if we had placed the thermistor in the center of the
display. However, the useers would not like that.

D

#### dalai lamah

Jan 1, 1970
0
Un bel giorno Spehro Pefhany digitò:
Unfortunately, that B (3435 +- 1%) is not very widely available. 8-(

Digikey gives me nine different models (they differ in resistance tolerance
and package):
P12007CT-ND
P12008CT-ND
P12009CT-ND
P12010CT-ND
P12011CT-ND
P12012CT-ND
P12013CT-ND
P12014CT-ND
P12011DKR-ND

Replies
17
Views
428
Replies
8
Views
367
Replies
3
Views
384
Replies
4
Views
1K
Replies
48
Views
3K